Looking back on my careers, all the companies I've worked for and all the great benefits I've earned, I have few regrets. The single one thing I do, however, wish I'd done differently is to have been a more aggressive seller in the stocks of the companies I have worked for.

It's too easy to accumulate stock in your own company. Many companies offer some kind of employee stock purchase plan. Some award stock to employees. Stock options are part of many companies' benefits packages. Does your company have a 401(k) plan? Chances are one of the first investment choices in your company's 401(k) plan is company stock.

Employees nearly always get an employee discount on their company's stock. Who can pass up the chance to buy an asset with appreciation potential at below market price?

Not me, and it's led me to my single largest regret of my investment career. I have only few regrets about holding on to losing stocks for too long. I have only a few about buying a stock on the way up only to find out I was buying at the top. Those are valuable lessons at the end of the day. Unwinding an enormously lopsided investment portfolio is a painful lesson. So painful, in fact, that it's become the single most painful thing I have ever done as an investor.

It could be for you too. If you let yourself become under diversified by virtue of your own company's stock, you may one day face one of the following prospects in order to diversify:

• Selling at a significant gain. This doesn't really seem like a problem, but had you been diversifying your investments in the first place it's a problem you would not have.
• Selling at a significant loss - insult added to injury.
• Selling with neither a loss nor a gain. OK, so you don't have a big tax bill and you have not lost money. Is having your money do nothing for all that time a good thing?

Had enough yet? If you're still not convinced, try this one...

How truly independent are you, financially, if both your income and your investments rely on the good fortunes of one company?